|Publication number||US7260516 B2|
|Application number||US 10/231,338|
|Publication date||Aug 21, 2007|
|Filing date||Aug 31, 2002|
|Priority date||Aug 31, 2001|
|Also published as||CA2458919A1, EP1430428A2, US20030046049, US20070255543, WO2003021498A2, WO2003021498A8|
|Publication number||10231338, 231338, US 7260516 B2, US 7260516B2, US-B2-7260516, US7260516 B2, US7260516B2|
|Inventors||Glen F. Chatfield, John G. Crandall|
|Original Assignee||Optimum Power Technology, L.P.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (31), Non-Patent Citations (2), Referenced by (6), Classifications (28), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present application claims priority to U.S. provisional patent application No. 60/316,463, filed Aug. 31, 2001, which is incorporated herein in its entirety and is currently pending. The present application also claims priority to U.S. provisional patent application No. 60/361,262, filed Mar. 2, 2002, which is incorporated herein in its entirety and is currently pending.
The present invention is directed to an apparatus, a system, and a method for creating one or more optimum solutions or designs. In particular, the present invention is applicable to a function that when plotted has multiple peaks or valleys indicating that good solutions exist in various solution regions. That function may represent the performance of a device that can be simulated, such as an engine. The present invention may employ design tolerances to reduce computing time and to terminate the optimization process.
Engine performance simulation software has become an integral part of the engine designer's toolkit. However, optimization of a particular design using such software is often difficult and time consuming. That is due primarily to the number of parameters required to adequately characterize the engine and the interdependency of these parameters on one another. The present invention describes apparatuses, systems, and methods that help to automate the engine design process and shorten the development time to meet specified performance goals.
The present invention is directed to a system, method and apparatus for optimizing a design. In accordance with one form of the present invention, there is provided a method for finding an optimum model that includes specifying a base model that includes: (i) a variable having a value, (ii) specifying a goal that identifies a characteristic of the base model that is to be optimized, (iii) specifying a tolerance that is a minimum amount that the variable can be changed, (iv) specifying a delta that is initially set to a maximum amount that the variable can be changed, (v) running the base model, (vi) identifying the current best model to be the base model, (vii) creating a plus model by setting the variable value to the current best model value plus the delta, (viii) running the plus model, (ix) creating a minus model by setting the variable value to the current best model value minus the delta, (x) running the minus model, (xi) setting a previous best model to the current best model and setting the current best model to the best of the current best model, the plus model and the minus model, (xii) repeating steps (vii) through (xii) if the current best model is different than the previous best model, (xiii) reducing the delta, (xiv) repeating steps (vii) through (xiv) if the delta is greater than or equal to the tolerance, and (xv) identifying the current best model as the optimum model.
The present invention is also directed to a system, method and apparatus for terminating an optimization.
Accordingly, the present invention provides solutions to the shortcomings of prior optimization apparatuses, systems and methods. Those of ordinary skill in the art will readily appreciate, therefore, that those and other details, features, and advantages of the present invention will become further apparent in the following detailed description of the preferred embodiments of the invention.
The accompanying drawings, which are incorporated herein and constitute part of this specification, include one or more embodiments of the invention, and together with a general description given above and a detailed description given below, serve to disclose principles of the invention in accordance with a best mode contemplated for carrying out the invention.
Reference will now be made in detail to the preferred embodiments, examples of which are illustrated in the accompanying drawings. It is to be understood that the Figures and descriptions of embodiments included herein illustrate and describe elements that are of particular relevance, while eliminating, for purposes of clarity, other elements found in typical computers and computer networks.
The present design optimization provides solutions to the shortcomings of certain previous design methods and systems. Those of ordinary skill in the art will readily appreciate that while embodiments of the present invention are described in connection with engine design, aspects of the invention are applicable beyond engine design. For example, the optimization techniques disclosed and claimed herein may be applicable to optimizations for various purposes and statistical analyses in general. The computational techniques disclosed and claimed herein may be applicable to applications in which such distributed processing is beneficial. The optimization techniques disclosed and claimed herein may be utilized for purposes other than engine optimization. The user interface described herein may also be applicable in a variety of useful applications. Thus, while certain embodiments of the present invention are directed to engine design, the present invention and aspects thereof are recognized to be beneficial in a variety of applications. Other details, features, and advantages of the design optimization will become further apparent in the following detailed description of the embodiments.
Any reference in the specification to “one embodiment,” “a certain embodiment,” or a similar reference to an embodiment is intended to indicate that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such terms in various places in the specification are not necessarily all referring to the same embodiment. References to “or” are furthermore intended as inclusive so “or” may indicate one or the other ored terms or more than one ored term.
While the present invention may be utilized to optimize a variety of complex apparatuses and processes, the following embodiments are directed to use of the present invention in optimizing an internal combustion engine. Such an engine has many attributes that contribute to the operation of the engine and many desirable goals. The attributes of an internal combustion engine include, for example, valve quantity and size, piston diameter and stroke, ignition timing, fuel delivery quantity and timing, and exhaust pipe diameter and length. Goals for operation of an internal combustion engine include, for example, fuel consumption, emissions, torque, and power.
In the following description, the term “variable set” is utilized to indicate a set of variable values that may be utilized to run a single simulation. A “run” or “simulation” is an act of running a simulation on a variable set under given test conditions. A “test procedure” is a set of test conditions under which a run occurs. A “result” is the value of characteristics or dependent variables from a simulation of a set of variables according to test conditions. The term “solution” refers to one or more runs utilized to evaluate goals. The term “pass” indicates a collection of solutions that is ranked to find the best variable set or sets. The term “optimum” is utilized to indicate a local optimum, which is the best variable set from the ranked set of solutions of a pass. A “model” is a set of variables that may be simulated and a “design configuration” is a model embodying a design. It is a benefit of the present invention that it is capable of providing multiple, diverse local optimums where such multiple, diverse optimum solutions exist.
A base model or a base design configuration is a starting definition of attributes or components to be modified by rules to create an optimized design. A “best model” is a model that most closely approximates one or more specified values when the directive of the goal is to match those values, a model that provides the highest resulting value when the goal is to maximize that value, and a model that provides the lowest resulting value when the goal is to minimize that value. The base design includes all attributes necessary to simulate the design. Design attributes may be stored in a design attribute database. The design utilized in the examples herein is an engine design so that the base design configuration in those engine examples is referred to as a “base engine.” Thus, those attributes may include dimensional data such as, for example, intake plenum dimensions, intake pipe length and diameter, exhaust pipe length and diameter, intake valve diameter, exhaust valve diameter, and cylinder length and diameter. Those attributes may also include other data such as, for example, sensed data including intake air pressure, exhaust air pressure, and throttle position. Attributes may furthermore be grouped logically by, for example, component such that an exhaust pipe length and an exhaust pipe diameter that are commonly used in combination may be grouped to define an exhaust pipe component. Those components may then be assigned names such that all the attributes for a component are grouped under a unique engine component name. The present optimization may then vary selected attributes and simulate operation of an engine having those varying attributes to achieve one or more goals.
At 102, an objective that contains one or more goals of the optimization is specified. The objective is a definition of the desired result of optimization. Goals may have at least three component parts: a characteristic, a directive, and a value. Each characteristic is an entity that is to be optimized, such as for example a performance characteristic of an engine. The directive instructs as to what is desired to be accomplished with the characteristic. For example, a directive may be an instruction to maximize the value of the characteristic, minimize the value of the characteristic, or match one or more desired values of the characteristic. The value provides an objective standard to compare the extent to which each design configuration approaches the desired result. In certain situations, goals that are minimized or maximized may not have an associated value, whereas goals that are to be matched typically would have at least one associated value.
The goal of the present example is the singular goal of achieving maximum power through the range of engine operation specified in the test procedure. Thus, the characteristic is power and the directive is to maximize that power.
The test procedure may, for example, specify a range of operation, a stepwise increment through the range, a number of engine cycles to simulate at each rpm step, a fuel utilized by the engine, a throttle position, and ambient conditions. The range may be, for example, 5000 rotations per minute (rpm) to 10,000 rpm and the increment may be 1000 rpm steps throughout the range. The fuel may be, for example, gasoline or diesel. Ambient conditions include air temperature, air pressure, and humidity at intake and exhaust points.
As has been mentioned, goals may be minimized, maximized, or matched to a desired value or a set of values. Where matching is desired, the value associated with the goal may be matched to, for example, a curve or set of values defining a curve. Goals may also be utilized as limits on the design. For example, a goal may be set with a high limit, a low limit, or a band having both high and low limits. Moreover, more than one goal may be established for a simulation. Thus, for example, a user may attempt to match a desired power curve while setting a particular high limit on carbon monoxide in the exhaust of an engine. In that example, all results producing a carbon monoxide level greater than the limit will be disregarded and the best fits to the power curve having a carbon monoxide level below the limit will be provided as results.
The high limit is the specification of a value or set of values for a parameter above which a design configuration is unacceptable. A high limit may, for example be placed on a parameter such as fuel consumption to prevent a resulting design from being overly inefficient as to fuel consumption. If the high limit is exceeded at any point, then the simulation may be considered to have failed for that variable set.
The low limit is the specification of a value or set of values for a parameter below which a design configuration is unacceptable. A low limit may, for example be placed on a parameter such as power to prevent a resulting design from having too little power. If a variable set produces a value that is below the low limit at any point during the simulation, then the simulation may be considered to have failed for that variable set.
A limit band includes a high and low limit, such that if the high limit is exceeded for a set of variables at any point during the simulation or the variable set produces a value that is below the low limit at any point during the simulation, then the simulation may be considered to have failed for that variable set.
A failed variable set typically is not used in the ranking of variable sets to determine the best result.
A strategy is a process used to obtain an objective. A strategy includes one or more variables and may or may not contain one or more constraints.
At 104, the variables to be optimized are specified. “Optimized” variables are those variables that are to be varied in the optimization simulations in order to accomplish the goals. Two variables are to be optimized in the embodiment described as an example herein; exhaust pipe length and exhaust pipe diameter. An initial value of each variable to be optimized may be assigned. Boundaries of values for which the simulation is to be run are then set. It has been determined for the present application that an exhaust pipe having a length of between 100 mm and 1000 mm is desired to fit the vehicle that the engine is operating. It has also been determined for the present application that an exhaust pipe having a diameter of between 100 mm and 200 mm is desired to fit the vehicle. Since only exhaust pipes having a length between 100 and 1000 mm will be considered, the boundaries for exhaust pipe length are 100 mm and 1000 mm. Similarly, the boundaries for exhaust pipe diameter are 100 mm and 200 mm. Where each variable represents an axis of a grid, the area encompassed by the boundaries may be viewed graphically and referred to as a “design space.”
The number of engines to be simulated may be limited, for practical purposes, by use of tolerances with variables or attributes that are permitted to vary during optimization. A tolerance may be set at a minimum increment desired for a variable such that variable values to be simulated will be limited to values falling at tolerance points. Without use of a tolerance, an infinite number of designs to be simulated would exist in any design space. By utilizing tolerances, infinitely small steps in the design space are eliminated and a finite number of simulations is forced to exist in a design space. When tolerances are used, variable values to be simulated are rounded to the nearest tolerance point so that values falling between those points are not simulated. A design tolerance may be equal to a manufacturing tolerance but may also be simply the amount of each step that a designer wishes the optimization to consider. For example, it may be desired to consider exhaust pipes in lengths having 10 mm increments and diameters having 1 mm increments. Thus, a tolerance for exhaust pipe length may be set at 10 mm and a tolerance for exhaust pipe diameter may be set at 1 mm. Graphically, the bounded design space may now be viewed as a grid having points located on every multiple of each tolerance. With regard to tolerances, a global tolerance may be set that is based upon a function of that variable such as the magnitude of the variable. Where desired, however, the tolerance for a variable may be set to any value. Tolerances may also be offset so that tolerance points may begin at other than zero or another multiple of the tolerance. Thus, for example, an exhaust pipe may be desired to be considered in 10 mm increments beginning a 25 mm, thereby providing a tolerance offset. The exhaust pipe lengths to be considered would then be in 10 mm increments from 25 mm (e.g., 25 mm, 35 mm, 45 mm, etc.).
Optimization having variables set at tolerances also provides a natural termination for the optimization program. Once all tolerance points around a point from which optimization is occurring have been simulated and do not yield a better value for the characteristic, the optimization may be terminated. Use of tolerance based simulation, furthermore, beneficially reduces the number of simulations run because variable values that are near each other are rounded to the same tolerance point and simulation of the same point need not be performed twice. Rather, the present invention is capable of recognizing that a variable set to be simulated is the same as a variable set previously simulated and so does not simulate that same variable set a second time.
At 106, constraints, including parametric equations, are specified. An initial design attribute may be defined as a constant value or by a parametric equation. Parametric equations are referred to herein as a type of constraint. A parametric equation defines an attribute in terms of one or more other attributes. An attribute that is defined by a parametric equation is not typically optimized. It may, however, change as variables being optimized change. For example, the entrance diameter of a pipe may be defined as being equal to the diameter of a port to which it connects. Alternately, a parametric equation could define the geometry of a component, such as a parallel pipe, by equating the exit diameter to the entrance diameter. Thus it is assured that only configurations in which inlet and outlet of the pipe are equal will be considered. As another example of a parametric equation, the stroke of an engine may be based on the displacement and bore to stroke ratio of the engine.
In an embodiment of the present invention, variable sets for design configurations in the design space are simulated in two steps. The first step, called exploration herein, simulates variable sets in various regions of the design space and the second step, called optimization herein, simulates design configurations in the most promising regions of the design space. In exploration, a small number of variable sets are selected to determine which region or regions in the design space are most promising. Thus for example, three values for each variable may be selected so as to be dispersed evenly across a range of values to be considered for each variable. In optimization, design configurations adjacent to the most promising design configurations explored in exploration are simulated to find optimum solutions in those regions.
At 108, attributes for a design of experiments are specified. The design of experiments attributes determine how many design configurations will be simulated in exploration 112 and optimization 114. Design of experiments attributes include a number of levels to be explored for each variable, the number of best runs desired for further consideration, the number of other regions desired for further consideration, and a number of runs limit. The level is a number of values for each variable that are to be considered during exploration. Viewed graphically with each variable defining an axis on a graph beginning with the lowest value to be considered and ending with the highest value to be considered, levels are a number of points to be simulated on each axis in exploration 112. The number of solutions to be simulated for exploration 112 is, thus, the product of the number of levels for each variable.
Global or local levels may be set for the variables when specifying the design of experiments 108. When global levels are assigned for all variables, the same number of values are considered for each variable. For example, a global level of 3 may be provided by default. Where three values are selected for each value, the number of design configurations that will be considered in exploration is 3n, where n is equal to the number of variables in the design configuration.
When local levels are set for each variable, the number of values to be considered during exploration is selected individually for each variable. Furthermore, a global level may be provided as a default and overriding local levels may be specified for one or more of the variables being explored. A level of zero may also be specified such that exploration 112 is disabled for a variable. Alternately, values may be specified by a user for consideration in exploration 112 or another technique may be utilized to select the values to be used in exploration 112.
A number of best runs may be specified to instruct optimization 114 as to how many design configurations are to be retained because they most closely approximate the goal. Those best design configurations often lie close to each other in a single region. The best design configurations may, however, lie in disparate parts of the design space and may result from optimizing more than one design configuration found in exploration 112.
It may be desired that optimum design configurations in one or more local optimum regions of the design space (regions not containing the best design configuration) be provided. For example, solutions in a local optimum region may be close enough to the goal to satisfy a designer and may be substantially more cost effective to implement. Thus, a number of other regions may be specified to provide so that design configurations in local optimum regions are also provided by optimization 114.
A number of runs limit may also be specified such that a limit is placed on the number of design configurations to be simulated. The number of runs limit may be accomplished by randomly selecting design configurations to be simulated from the total number of design configurations that could be simulated. A random number seed may, furthermore be specified in a computer system so that the same design configurations may be simulated by choosing the same seed and different design configurations may be simulated by selecting a different seed.
Optimizations are specified at 110. In optimization, adjacent design configurations are simulated by stepping from a base design simulation to adjacent design configurations to find optimum solutions in each region selected in exploration 112. In the optimization specification phase, a determination of whether and how variables are to be combined in optimization 114 is made. As has been explained hereinbefore, variables may be optimized individually or in combination. Steps may be applied during optimization 114 as “individuals” where only one variables is changed when simulating adjacent design configurations or as “combinations” where a combination of at least two variables are changed when simulating adjacent design configurations.
It may be noted that all variables may be combined or uncombined or subsets of the variables may be combined in one or more combinations.
In addition, step and step delta start and end factors may be specified, a threshold may be specified, an optimization methodology may be specified, and a limit on the number of runs for each pass of the optimization may be specified. Step size is defined for each variable. A step, in turn, defines an area on a grid, plus or minus from a base point, that will be considered in optimization. One useful step size is the distance between exploration points, which causes optimization to occur from a base point to each surrounding exploration point. Step delta start and end factors may be defined as percentages of the step or portions of the step. A step delta start factor defines the distance from a base point, as a portion of a step, at which the first optimization pass will occur. A step delta end factor defines the distance from a base point, as a portion of a step, at which the last optimization pass will occur if the optimization is not terminated by other means. Moreover, one or more variables may be eliminated from the optimization 114 because those variables were only necessary for exploration 112.
The step delta factors are used by the optimization to determine a new value for a variable set based on a portion of the distance between two adjacent points on the exploration grid. The threshold is evaluated at each pass to determine whether the optimization is complete. The optimization may thus terminate upon reaching a threshold or may terminate prior to reaching a threshold for other reasons. For example, another reason that optimization may terminate is because design configurations for all tolerances in the design space surrounding the base point have been simulated and no better result was found.
The optimization methodology for the present embodiment is based on a steepest decent analysis. Alternately, a downhill simplex or other form of analysis may be utilized. Downhill simplex does not allow any combinations and may not perform ideally in combination with tolerances, since it depends upon small changes to keep it progressing.
A limit for the number of runs to be simulated in each pass may be specified if such a limit is desired and a random number seed may be specified in case the limit is exceeded.
During exploration 112, the design space is explored combining all the variables based upon the levels of each variable or other specified values. A baseline simulation may be run initially. The baseline simulation may be run for comparison to other simulated configurations. Thus, for example, an engine for a vehicle may be optimized for power by varying exhaust pipe length and diameter. The simulation may utilize values from the baseline simulation that define a complete engine for all design configurations while varying values for exhaust pipe length and diameter only. Thus, if an engine to be optimized is currently utilizing an exhaust pipe that is 700 mm long and 150 mm in diameter, power may be determined for that configuration over a desired range of engine speeds for the baseline simulation. The range of engine speeds for this example will be 5000 to 10,000 rpm. The result of the baseline simulation may then be compared to each other variation of exhaust pipe length and diameter examined during the optimization.
It is not necessary, however, to run a baseline simulation. Simulation results may simply be ranked to determine which configurations of the variables are best. Exploration 112 may calculate the result (in the present example engine power) at the various defined points within the boundaries set for the variables (in the present example exhaust pipe lengths from 100 mm to 1000 mm and diameter from 100 mm to 200 mm). Those results may then ranked to determine which configurations of the variables provide the best results.
In a certain embodiment wherein duplicate variable values may be produced by the method described in
At 248, if counter “M” is less than the level selected for second variable “diameter,” then counter “M” is incremented at 250 and the process returns to 242 to calculate the desired diameter value for the next step. When counter “M” is equal to the level selected for second variable “diameter” then the process proceeds to 252. At 252, if counter “N” is less than the level selected for first variable “length,” then counter “N” is incremented at 254 and the process returns to 236 to calculate the desired length value for the next step. When counter “N” is equal to the level selected for first variable “length” then the process ends at 256.
It should be recognized that values calculated in the design of experiments value determination method 230 of
At 134, the starting value is checked to determine whether it is greater than the maximum boundary for that variable. If the starting value is greater than the maximum boundary set for that variable then the starting value is given the value of the maximum boundary at 136. At 138, the starting value is set equal to the integer of the starting value divided by the tolerance and that value is multiplied by the tolerance. A value other than an integer may alternately be specified at 138. Thus, at 138 the starting value is always set at a multiple of the tolerance. As an example, if an exhaust pipe length of 1005 mm is input, the maximum length to be considered is 1000 mm, and the tolerance is 10 mm, then the starting value will be set equal to the 1000 mm maximum length at 136. The integer of (1000 mm / 10 mm) * 10 mm is 1000 mm. Thus it is confirmed that 1000 mm is a multiple of the tolerance of 10 mm.
Where a rounded integer function is used at 138 and a boundary is not set at a multiple of the tolerance, it is possible for the result of the equation of 138 to fall outside of the boundary. Therefore, at 140 and 142, the method will subtract one tolerance from the starting value if the starting value is greater than the maximum boundary set.
At 144, the starting value is checked to determine whether it is less than the minimum boundary for that variable. If the starting value is less than the minimum boundary set for that variable then the starting value is given the value of the minimum boundary at 146. At 148, the starting value is set equal to the integer of the starting value divided by the tolerance and that value is multiplied by the tolerance. Thus, at 148 the starting value is always set at a multiple of the tolerance. At 150 and 152, the method will add one tolerance from the starting value if the starting value is less than the minimum boundary set and at 154 the tolerance method terminates.
During exploration 112 sets of values for the variables spread evenly within the boundaries may be generated and simulations run for each of those sets. In the present embodiment, all sets of values to be explored are calculated first and then each simulation is run. A benefit to that ordering is that multiple simulations may be run simultaneously. That ordering is particularly advantageous where the simulations are performed on a network of computers wherein multiple processors are available to run simulations simultaneously. Simulations may, however, alternately be run as the variable values are determined.
If the number of runs created in exploration 112 exceeds the number of runs limit, then variable sets are either selected or deselected until the number of simulations to be run is equal to the runs limit. Selection or de-selection may be based on a randomization. Moreover, the randomization may be seed based such that the results are repeatable or modifiable as desired.
Step size is based on the step delta specified during specification of optimization 110. The optimization may continue the process of migration and shrink until a step delta end factor has been reached or design configurations for all tolerances adjacent to the base point have been simulated and no better result of the characteristic was found. Thus, for example, the step delta start factor may be 64% of the step delta and the step delta end factor may be 1% of the step delta. Designs may, thereby, be simulated 64% of the step from the base point initially, then 32% of the step from the base point, 16% of the step from the base point, 8% of the step from the base point, 4% of the step from the base point, 2% of the step from the base point, and 1% of the step from the base point as shrinkage passes occur. As has previously been noted, during migration, engine designs from previous passes that overlap on the current pass may not be selected for regeneration since they were previously generated.
The optimization begins at 302 by setting a shrink factor to the step delta start factor previously specified. It has been found through experimentation that a first pass having a shrink factor that is equal to 64% of the step size between exploration points is beneficial and so a 64% shrink factor will be used in the following example and the distance between exploration points for each variable will be used as the step size for each variable.
At 304, values for simulations propagating from the current base point are determined. As may be seen in
It is noted that where two or more variables are considered in a simulation, any two or more variables may be combined while other variables are considered individually or separately in combination. Furthermore, the present invention contemplates dynamic combination of variables based on the degree of improvement in the result from the best solution of the previous pass. The dynamic combination could include, for example, any variable that changed in the best result of the previous pass combined with other unchanged variables. Alternately, any or all of the variables that changed in the best result of the previous pass may be combined. Moreover, any or all of the variables that changed in the last pass may be combined with any or all of the unchanged variables. For example, each unchanged variable may be combined with a combination of any or all of the variables that changed in the previous pass.
At 306, the tolerance method illustrated in
As was previously discussed, variable sets that have been simulated may be stored in a database and newly determined variable sets may be compared to those previously simulated variable sets so that duplicate variable sets may be discarded and not simulated for a second time. Thus, at 308, the variable sets determined at 304 and 306 are compared to variable sets already simulated and at 310 non-duplicative variable sets are saved to the database.
At 311, if the number of runs created in an optimization pass exceeds the number of runs limit, then variable sets are either selected or de-selected until the number of simulations to be run is equal to the runs limit. Selection or de-selection may be based on a randomization. Moreover, the randomization may be seed based such that the results are repeatable or modifiable as desired.
At 312, a determination is made as to whether any additional simulations exist to be simulated around the current base point. Because the present embodiment is tolerance based, as solutions passes are performed a time may arise when all multiples of the tolerance around a base point have been explored. When all tolerance multiples around a base point have been explored, the solutions process will proceed to 322. If all tolerance multiples around a base point have not been explored the solutions process will proceed to 314.
At 314, simulations are run on each variable value set in a pass, and at 316 the latest simulation results are compared to previous simulation results to find the best simulation result to that time.
At 318, a determination is made as to whether one of the results of the last solutions pass is better than the previous best result and are greater than the previous best result by more than the threshold. If one of the results in the last solutions pass is the best result, then the base point is reset to the new point having the best result at 320 and the process returns to 304. If none of the results of the last solutions pass is the best result, the solutions process proceeds to 322. At 322, the current percentage is divided by two or some other factor and at 324 a decision is made as to whether the current percentage is less than the step delta end factor. If the current percentage is greater than or equal to the step delta end factor, the process returns to 304 to make another solutions pass at, for example, half the distance from the base point. If the current percentage is less than the step delta end factor the optimization terminates at 326. Of course, terminating at a percentage of the step delta end factor is not necessary, but it beneficially prevents simulations from continuing past a point where the benefit derived from further simulation is minimal.
The optimization results may be normalized. For example, results may be normalized to account for differences in the magnitude of each goal. Thus a normalized result might be based on the percent of the average result. Results may also be weighted so that one goal is given a greater weighting than another where goals are of varying importance.
One technique that may be used in connection with goals is referred to herein as “match design.” Match design is a specification of a set of values, such as power or fuel consumption, for evaluating the results of a simulation by computing the least squares fit to produce an error value. Error values may furthermore be normalized, for example, to account for differences in the magnitude of the results for each goal. Thus a normalized error value might be based on the percent that the average results vary from a desired match. Error values may also be weighted such that one error value is given a greater weighting than another where goals are of varying importance.
Hold 352 is a way for the user to temporarily pause the optimization. “Release” appears in place of “Hold” on the explorer pop-up menu 350 when the optimization is currently on hold. Priority 354 is the method for changing which optimization will run if more than one optimization is available to be processed.
Dynamic priority is an automatic process that the optimization uses to determine its own priority in relation to other optimizations that may be running concurrently. Dynamic priority could, for example, be the negative of the number of runs created in a pass, thus giving higher priority to a pass having a smaller amount of runs. Mark done 356 provides a way for the user to abort the optimization.
Optimize status 358 produces monitoring information when selected. For example, selection of optimize status 358 may cause the display of
In a computer system or network of computer systems, simulations may run as a background task so as not to interfere with user activity. While the optimization is occurring, monitoring information 400 may be invoked. As illustrated in
History may be provided for a completed optimization or an optimization in progress. The summary table 408 and detail table 410 are samples of history that may be provided. That history can be exported, printed or shown as a graph.
The present invention may be performed by various methods including, for example, manually or by a general purpose computer. A computer system 420 for performing optimization on a distributed network is illustrated in
Utilizing the network, when a group of simulations are ready to be performed, each simulation of a set of variables may be executed on a processor attached to the network. Each simulation may be placed in a table along with attributes such as, for example, what processor is performing the simulation, what time the simulation was placed in the table, whether the simulation has been completed, etc. Processors on the network may then access the table and perform the simulations as those processors are available. The simulation itself may be represented by a definition of a set of rules under which the simulation is to be performed (e.g., a particular commercially available engine), the variables to be optimized (e.g., exhaust pipe length and exhaust pipe diameter), and the goal (e.g., maximization of power over a range of 2000-10,000 rpm). In one embodiment, the processors are workstations available on desktops to perform tasks required by a user at each desktop. Each workstation that is not employed in a higher priority task by a user at its desktop, however, is available to perform one or more simulations. Thus an existing network of individual computers may perform their normal tasks and, when not employed in higher priority tasks, may perform simulations in the background.
A pair of default tolerance dialog boxes 556 are also included in the global screen 550. The default tolerance dialog boxes 556 provide spaces in which factors that are used to compute a default tolerance factor and a textual description of the formula used to compute default tolerance may be entered. The default tolerance factor and formula determine the default tolerance for every variable. At 558, a textual description of the level is included. “Normal” in the context of the level textual description indicates a default level of 3. Thus, the default levels dialog box 552 and the textual description of the level 558 are tied such that a change in one will cause the other to change.
While the present invention has been disclosed with reference to certain embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the scope of the present invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims, and equivalents thereof.
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|U.S. Classification||703/14, 700/44, 703/2, 702/105, 342/378, 702/27, 700/28, 702/19, 702/151, 700/54|
|International Classification||G06Q10/00, G05B13/04, F02D41/14, G05B17/02, G06F17/50|
|Cooperative Classification||G05B13/042, G06F17/50, G05B17/02, G06F2217/08, G06Q10/04, F02D2041/1433, F02D41/1406, F02D2041/1423|
|European Classification||G06Q10/04, G05B13/04B, F02D41/14B10, G05B17/02, G06F17/50|
|Aug 31, 2002||AS||Assignment|
Owner name: OPTIMUM POWER TECHNOLOGY, L.P., PENNSYLVANIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:CHATFIELD, GLEN F.;CRANDALL, JOHN G.;REEL/FRAME:013263/0215
Effective date: 20020830
|Jul 29, 2008||CC||Certificate of correction|
|Feb 21, 2011||FPAY||Fee payment|
Year of fee payment: 4
|Feb 10, 2015||FPAY||Fee payment|
Year of fee payment: 8